php计数器增量错误

Question

As i am trying to increment the counter to plus 1 every time when the user clicks on the image. I have written the following code but it says some error "Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in C:\\xampp\\htdocs\\tkboom\\includes\\core.php on line 72". Can anyone look into this where i made a mistake..

Actually i have created 2 php files one for incrementing the counter and one for displaying the counter. In core.php file i have written the function and for displaying the count i have created a file called view.php

core.php
    function GenerateCount($id, $playCount) {
            global $setting;
            $counter_query = "SELECT hits FROM ava_games WHERE id=".$_GET['id']."";
            $counter_res = mysql_query($counter_query);
            while($counter_row = mysql_fetch_array($counter_res)){
               $counter = $counter_row['hits'] + 1;
               $update_counter_query = "UPDATE ava_games SET hits=".$counter." WHERE id=".$_GET['id']."";
               $playCount = mysql_query($update_counter_query);
               $playCount = $row['hits'];
            }
            return $playCount;

    // Get count END
    }

view.php

<?php

$sql = mysql_query("SELECT * FROM ava_games WHERE published=1 ORDER BY id desc LIMIT 30");
while($row = mysql_fetch_array($sql)) {

    $url = GameUrl($row['id'], $row['seo_url'], $row['category_id']);

    $name = shortenStr($row['name'], $template['module_max_chars']);

    $playRt = GenerateRating($row['rating'], $row['homepage']);

    $playCt = GenerateCount($row['id'], $row['hits']);


    if ($setting['module_thumbs'] == 1) {
        $image_url = GameImageUrl($row['image'], $row['import'], $row['url']);

        $image = '<div class="homepage_game"><div class="home_game_image"><a href="'.$url.'"><img src="'.$image_url.'" width= 180 height= 135/></a></div><div class="home_game_info"><div class="home_game_head"><a href="'.$url.'">'.$name.'</a></div></div><div class="home_game_options"><img class="home_game_options_icon" src="'.$setting['site_url'].'/templates/hightek/images/joystick-icon.png" /> &nbsp;'.$playRt.' <b>|</b> '.$playCt.' plays &nbsp;</div></div>';
        echo $image;
    }



    }

?>

Answer 1

That most likely means that there's an error in the sql statement. You can get more information about the error via mysql_error() .
In its simplest form:

$counter_res = mysql_query($counter_query) or die(mysql_error());

(edit: ...simplest form, but with this approach you don't give the application a chance to react to the problem, "die" as in "dead". And mysql_error() can leak too much information to a user of your webservice/website, see https://www.owasp.org/index.php/Top_10_2007-Information_Leakage_and_Improper_Error_Handling )

Your code is also prone to

• sql injections , because the $_GET parameter is put into the statement without sanitizing it first
• race conditions because you have a compound operation consisting of one SELECT and one UPDATE without any locking mechanism.

Answer 2

This is because you get the error in your SQL query.
I'd change it a little bit:

$counter_query = 'SELECT hits FROM ava_games WHERE id = ' . (int)$_GET['id'];

to make sure you always compare id against integer value.

Answer 3

After all, this query does not look good. First point: why are you using two queries to increment a value? UPDATE ava_games SET hits=hits+1 WHERE id=".$_GET['id']."" should do this in one step. Second point: have you heard about SQL injections? Escape or cast $_GET['id'] to avoid surprises ;)

Answer 4

If mysql_query returns a Boolean, your query failed.

Presuming id is the primary key, you can use the following function to update on a database level which will prevent race conditions:

function GenerateCount($playCount) {
    global $setting;
    $update_counter_query = "UPDATE ava_games SET hits=hits + 1 WHERE id=".intval($_GET['id'])."";
    mysql_query($update_counter_query) or die(mysql_error());
    $counter_query = "SELECT hits FROM ava_games WHERE id=".intval($_GET['id'])." LIMIT 1";
    list($playCount) = mysql_fetch_row(mysql_query($counter_query));
    return $playCount;

// Get count END
}

also note the intval() around the $_GET variable to prevent SQL injection

Answer 5

Convert the value in int first like that:

function GenerateCount($playCount) {
    global $setting;
        $counter_query = "SELECT hits FROM ava_games WHERE id=".$_GET['id']."";
        $counter_res = mysql_query($counter_query);
        while($counter_row = mysql_fetch_array($counter_res)){
        $counter = intval($counter_row['hits']) + 1;
        $update_counter_query = "UPDATE ava_games SET hits=".$counter." WHERE id=".$_GET['id']."";
        $playCount = mysql_query($update_counter_query);
        $playCount = $row['hits'];
    }
    return $playCount;

// Get count END
}

and check link:

Convert into int